Method of maintaining a column of liquid within an open-ended tube, and a tube device for carrying out the method

ABSTRACT

A method of and device for maintaining a column of liquid comprising comprises a straight open-ended tube, and a plug of porous material frictionally located within the bore of the tube at a predetermined distance from one end of the tube. A column of liquid may be maintained within such a tube by placing the said one end of the tube in communication with a supply of liquid, and applying suction to the other end of the tube to draw a column of liquid into the tube to a level above the plug. The suction is then removed to allow the column of liquid to fall until its surface contacts the plug, whereupon the remaining column of liquid is maintained by interaction of the respective physical characteristics of the liquid, the plug, and the tube.

United States Patent Betts et a].

{45] June 24, 1975 I METHOD OF MAINTAINING A COLUMN 2376,23: 5/1945 Cohn I 5. 73/4254 P OPENENDED 1423.173 7/1947 Brady et all. 73/4254 P gg FOR 2,692,503 l0/l954 Crccelius .7 73/4254 P 1734.358 5/1973 Bergeron 73/4256 CARRYING OUT THE METHOD [76] Inventors: Peter Alan Betts, 40 Oldfield Rd., Primary E.\'aminer.loseph Scovronek Chesire, Sandbach; Kenneth Assistant Examiner-Dale Lovercheck Stephenson, l8 Hodder Ave, Attorney, Agent, or Firm-Ross. Ross & Flavin Littleborough, both of England 1221 Filed: Jan. 24, 1973 I ABSTRACT I21] APPL No; 326,233 method of and device for maintaining a column of liquid comprising comprises a straight open-ended tube, and a plug of porous material frictionally located [30] Foreign Application Priority Data within the bore of the tube at a predetermined dis- July 4, 1972 uni Kingdom 3 27 72 tance from one end of the tube. A column of liquid may be maintained within such a tube by placing the [52] 0.5. CI 23/230 R; 23/259; 23/292; said one end f the u in m uni ati n ith a sup- 73/425 4 P; 141/3] ply of liquid. and applying suction to the other end of [5 l] Int. Cl BOlI 3/02; GOlf 13/00; GOln 1/10 the tube to draw a column of liquid into the tube to a [58] Fi ld f S h 23/259. 230 R, 230 B. 292; level above the plug. The suction is then removed to 73/4254 P, 425.6, 425.4 R; 222/]89; allow the column of liquid to fall until its surface 62/5] 1; |4|/31; 55/386 contacts the plug, whereupon the remaining column of liquid is maintained by interaction of the respective [56] References Cited physical characteristics of the liquid, the plug, and the UNlTED STATES PATENTS 2.348,83l 5/l944 Mathis 73/4254 P 1 Claim, 2 Drawing Figures METHOD OF MAINTAINING A COLUMN OF LIQUID WITHIN AN OPEN-ENDED TUBE, AND A TUBE DEVICE FOR CARRYING OUT THE METHOD This invention concerns a method of maintaining a column of liquid within an open-ended tube, and a tube device for carrying out the method.

It is common practice when transferring liquids for or during analysis, for a sample of the liquid to be drawn into a pipette or tube by suction applied to the upper end thereof, the column of liquid within the pipette or tube being maintained by the suction effect created by closing the upper end of the pipette, the desired height of the column of liquid first having been achieved by fine adjustment of the suction applied to the pipette or tube.

This method of transferring sample liquids is particularly common in pathological analysis where sample liquids are transferred by means of a pipette having a length of flexible hose attached to its upper end. A technician transferring a sample liquid by this means places the free end of the flexible hose in his mouth and, by sucking through the hose, draws a column of the liquid into the pipette. The height of the column of liquid is adjusted by carefully controlling the suction and, once the desired height has been achieved, the flexible tube is squeezed to close off the upper end of the pipette from atmosphere so as to maintain the column of liquid. The pipette is then transferred from the liquid to a suitable receptacle, such as a test tube, whereupon the flexible hose is released to allow the column ofliquid to fall from the pipette into the receptacle.

A disadvantage of this method of transferring liquids is that establishing and maintaining the column of liquid at the required level requires skill and, particularly where a number of liquid samples are required, is tedious and time consuming.

An object of the present invention is to provide an improved method of maintaining a column of liquid within an open-ended tube.

A further object of the invention is to provide a tube device for use with the method of the invention.

With the first of these objects in view, the present invention provides a method of maintaining a column of liquid within an open-ended tube, comprising placing within the tube a plug of porous material, positioning the plug at a predetermined distance from one end of the tube corresponding to the height of the desired column of liquid, placing the said one end of the tube in communication with a supply of liquid, applying to the other end of the tube suction sufficient to draw a column of the liquid into the tube to a position beyond the plug, removing the suction and allowing the column of liquid to fall until the liquid surface contacts the plug, the remaining column of liquid being thereupon maintained by interaction of the respective physical characteristics of the liquid, the plug, and the tube.

With the second object in view, the present invention also provides a tube device comprising a substantially straight tube having a plug of porous material within its bore.

The plug is preferably made from a fibrous material, but may consist of any convenient porous material.

The position of the plug may be adjustable to any position in the bore of the tube.

Alternatively, the plug may be at a fixed position relative to the length of the tube.

The tube is conveniently in the form of a pipette.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

HO. 1 is a side view ofa tube device according to the invention; and

FIG. 2 is an enlarged longitudinal medial section showing a detail thereof.

The device shown in the drawings, comprises a substantially straight tube 11 with a plug 13 within its bore 12. A graduation scale 14 is provided along tube 11 which is intended to be used as a pipette in the pathological testing of liquid samples. The plug 13 consists of a fibrous material having capillary attraction for blood and is positioned a predetermined distance from the starting point of the scale 14 at the lower end of the tube 11, whereby the device is prepared ready for use in maintaining a column of blood of an amount suitable for conducting a particular test.

In use, the lower end 11a of tube 11 is placed in communication with a supply of blood and suction is applied, by any convenient means which is not shown, to the other end of tube I I to draw a column of blood into the tube bore 12 to a position above plug 13. The suction is then removed and the column of blood falls until its surface comes into contact with plug 13. At this point, capillary attraction between the blood and the plug 13 prevents the remaining column of blood from flowing from the tube 11.

The suction may be applied to the tube, for example, by any suitable pump connected to the upper end of tube II by means of a length of flexible hose. Alternatively, a length of hose may be attached by one end to tube 11 and a technician may suck through the other end of the hose in a manner similar to that previously described, but without having to accurately position the blood surface against the graduation scale.

It will be appreciated that the device described above is illustrative and not limitative of the invention and modifications may be made thereto without departing from the scope of the invention.

For example, the plug may consist of any material having a capillary attraction for a liquid with which the device is intended to be used and, in this connection, the plug may be made of a material of other than fibrous structure, for example a material of open-cell structure.

The plug may also be movable within the bore of the tube, instead of being in a pre-set fixed position.

The tube may also be in the form of a pipette.

We claim:

1. A method of maintaining a column ofliquid within an open-ended tube comprising the steps: placing within the tube a plug of porous material having a capillary attraction for a liquid, positioning the plug at a predetermined distance from one end of the tube corresponding to the height of the desired column of liquid, placing the one end of the tube in communication with a supply ofliquid, applying to the other end of the tube suction sufficient to draw a column of liquid from the liquid supply into the tube to a position wherein its surface level lies above the plug, terminating the suction to lower the column of liquid until the liquid surface contacts the plug, and maintaining the remaining column of liquid by capillary attraction between the liquid and the plug. 

1. A METHOD OF MAINTAINING A COLUMN OF LIQUID WITHIN AN OPEN ENDED TUBE COMPRISING THE STEPS OF PLACING WITHIN THE TUBE A PLUG OF POROUS MATERIAL HAVING A CAPILLARY ATTRACTION FOR A LIQUID, POSITIONING THE PLUG AT A PREDETERMINED DISTANCE FROM ONE END OF THE TUBE CORRESPONDING TO THE HEIGHT OF THE DESIRED COLUMN OF LIQUID, PLACING THE ONE END OF THE TUBE IN COMMUNICATION WITH A SUPPLY OF LIQUID, APPLYING TO THE OTHER END OF THE TUBE SUCTION SUFFICIENT TO DRAW A COLUMN OF LIQUID FROM THE LIQUID SUPPLY UNTO THE TUBE TO A POSITION WHEREIN ITS SURFACE LEVEL LIES ABOVE THE PLUG, TERMINATING THE SUCTION TO LOWER THE COLUMN OF LIQUID UNTIL THE LIQUID SURFACE CONTACTS THE PLUG, AND MAINTAINING THE REMAINING COLUMN OF LIQUID BY CAPILLARY ATTRACTION BETWEEN THE LIQUID AND THE PLUG. 